Using first-principles calculations within the generalized gradient approximation （GGA） ＋U framework, we inves- tigate the effect of C doping on the structural and electronic properties of LiFePO4. The calculated f...Using first-principles calculations within the generalized gradient approximation （GGA） ＋U framework, we inves- tigate the effect of C doping on the structural and electronic properties of LiFePO4. The calculated formation energies indicate that C doped at O sites is energetically favoured, and that C dopants prefer to occupy 03 sites. The band gap of the C doped material is much narrow than that of the undoped one, indicating better electro- conductive properties. To maintain charge balance, the valence of the Fe nearest to C appears as Fe3＋, and it will be helpful to the hopping of electrons.展开更多
Rational design and controllable synthesis of practical electrodes with high sta bility and activity at high current density for a hydrogen evolution reaction(HER)are critical for renewable and sustainable energy conv...Rational design and controllable synthesis of practical electrodes with high sta bility and activity at high current density for a hydrogen evolution reaction(HER)are critical for renewable and sustainable energy conversion.However,high-performance TiO_(2)-based electrocatalysts for HER are quite limited,and the cat alytic active centers still remain elusive.Herein,a simple strategy is demonstrated for the synthesis of TiO_(2)-carbon composite(TiO_(2)/C)with high HER performance and stability.The remarkable HER performance of TiO_(2)/C can be ascribed to the doping of carbon atoms,which leads to stronger hybridization of Ti 3d and O 2p orbitals,thus substantially improving the electrocatalytic efficiency.This study elucidates that the hydrogen evolution activity of oxide electrocatalysts can be largely improved by regulating their electronic structures by doping carbon atoms and also provides an effective strategy for designing heterostructured electro catalysts with high catalytic activity and stability at high current density for HER.展开更多
The electron structure and optical properties of C-TiO_(2)(001)surface under external electric field were studied by DFT method.After carbon doping,a new impurity level is introduced in the bandgap region of TiO_(2)(0...The electron structure and optical properties of C-TiO_(2)(001)surface under external electric field were studied by DFT method.After carbon doping,a new impurity level is introduced in the bandgap region of TiO_(2)(001)surface,and leads to the decrease of band gap,contributing to the shift of optical absorption to the visible region.When external electric field is applied across the C-TiO_(2)(001)surface,the band gap is further reduced with the increase of the electric field intensity from 0.1 eV to 0.5 eV.The electric field over 0.5 eV induces the electronic polarization.The spin-up bands show a gap,while spin-down electrons correspond to a metallic state.The energy gap of spin-up band decreases with increasing the electric field from 0.7 eV to 1.0 eV.The optical absorption of C-TiO_(2)(001)shifts to long wavelength compared with pure TiO_(2)(001).The electric filed make the optical absorption red-shift further,and the shift increases with an increase of the electric field,especially in the range of 0.7 eV-1.0 eV.The results show that the combined effect of carbon doping and electric field can enhance the photocatalytic activity of TiO_(2)(001)surface in visible region.展开更多
The design and development of a highly robust catalyst for energy production and environmental abetment are gaining much attention in the field of visible-light-driven catalysis.This work demonstrates the fabrication ...The design and development of a highly robust catalyst for energy production and environmental abetment are gaining much attention in the field of visible-light-driven catalysis.This work demonstrates the fabrication of a series of hierarchical macroporous mixed-phase TiO_(2)on the surface of B-doped g-C_(3)N_(4)(BCN).The physicochemical properties such as crystallinity,morphology,chemical environment,and optical and electronic properties of the as-synthesized materials were analysed by using different analytical techniques.PXRD and HRTEM data revealed the growth of mixed-phase TiO_(2)(anatase and rutile)on the BCN surface,mimicking P25 in the case of the best photocatalyst(TBCN-8).The catalytic activity of the as-synthesized materials was tested towards H2O_(2)production(110μmol h-1)and phenol oxidation(87% of 20 ppm phenol solution)under visible light.Higher photocurrent,lower impedance arc,and lower PL intensity suggest a lower electron-hole recombination rate in the case of TBCN-8,elucidating the best catalytic performance by the material.This work validates the facile fabrication of macroporous TiO_(2)/BCN nanocomposites and their visible-light-driven catalytic activity based on both the p-n heterojunction and Z-scheme mechanism.展开更多
As a promising hydrogen evolution reaction(HER)electrocatalyst,molybdenum carbide materials have attracted great attention owing to their Pt-like electronic structure.The morphology control of Mo_(2)C usually involves...As a promising hydrogen evolution reaction(HER)electrocatalyst,molybdenum carbide materials have attracted great attention owing to their Pt-like electronic structure.The morphology control of Mo_(2)C usually involves complicated procedures,and porous structures are desirable for electrocatalytic applications.Herein,we present a facile acid-directed synthesis strategy forβ-Mo_(2)C nanoparticles embedded in a nitrogen doped carbon matrix(β-Mo_(2)C/NC)with controllable morphologies through heat treatment of Mo-melamine complexes for electrocatalytic HER applications.It is found that the applied acid can effectively tune the morphology of Mo-melamine complexes,and thus the finalβ-Mo_(2)C/NC materials.With oxalic acid,the as-preparedβ-Mo_(2)C/NC materials possess a porous structure and high surface area(23.3 m^(2)g^(-1)),leading to distinguished electrocatalytic HER activities in both acidic and alkaline media,requiring low overpotentials of 152 and 135 mV vs.reversible hydrogen electrode(RHE)to reach a current density of-10 mA cm^(-2),with a Tafel slope of 58 and 56 mV dec^(-1),respectively.The synthetic route proposed in this work may offer a new thinking for the morphology-controllable synthesis of transition metal carbide materials for heterogeneous(electro)catalysis applications.展开更多
By using a combined method of density functional theory and non-equilibrium Green＇s function formalism,we investigate the electronic transport properties of carbon-doped armchair phosphorene nanoribbons（APNRs）.The ...By using a combined method of density functional theory and non-equilibrium Green＇s function formalism,we investigate the electronic transport properties of carbon-doped armchair phosphorene nanoribbons（APNRs）.The results show that C atom doping can strongly affect the electronic transport properties of the APNR and change it from semiconductor to metal.Meanwhile,obvious negative differential resistance（NDR） behaviors are obtained by tuning the doping position and concentration.In particular,with reducing doping concentration,NDR peak position can enter into m V bias range.These results provide a theoretical support to design the related nanodevice by tuning the doping position and concentration in the APNRs.展开更多
Hierarchical hollow-structured magnetic–dielectric materials are considered to be promising and competitive functional absorbers for microwave absorption(MA).Herein,a hierarchical hollow hydrangea multicomponent meta...Hierarchical hollow-structured magnetic–dielectric materials are considered to be promising and competitive functional absorbers for microwave absorption(MA).Herein,a hierarchical hollow hydrangea multicomponent metal oxides/metal-carbon was designed and successfully produced via a facile self-assembly method and calcination process.Adequate magnetic NiO and Ni nanoparticles were suspended within the hollow hydrangea-like nitrogen-doped carbon matrix(HH N-NiO/Ni/C),constructing a unique hierarchical hollow structured multicomponent magnetic–dielectric MA composite.The annealing temperature and oxidation time were carefully regulated to investigate the complex permittivity and permeability.HH N-NiO/Ni/C delivers exceptional MA properties with maximum reflection loss of–45.8 dB at 1.7 mm thickness and displays a wide effective absorption frequency range of 5.6 GHz.The superior MA performance can be attributed to the following aspects:(1)The hierarchical hollow multicomponent structure offers plentiful of heterojunction interfaces triggering interfacial polarization;(2)nitrogen doped-carbon(N-C)facilitates the conductive loss by the unique electron migration path in the graphitized C and NiO/Ni;(3)magnetic NiO/Ni nanoparticles homogeneously dispersed within N-C form extensive C skeleton and strengthen the magnetic response ability;(4)hierarchical hollow wrinkled structures possess a large interspace and heterogeneous interface improving polarization loss and enhancing multireflection process and the unique structure satisfies magnetic and dielectric loss simultaneously resulting from synergistic effects of different components within the composites.展开更多
Enormous endeavors have been made to cope with microwave pollution and energy crisis.Here,porous nitrogen-doped C/TiO_(2) composites with absorption/shielding/supercapacitor functions were derived from MXene/polyanili...Enormous endeavors have been made to cope with microwave pollution and energy crisis.Here,porous nitrogen-doped C/TiO_(2) composites with absorption/shielding/supercapacitor functions were derived from MXene/polyaniline.It was discovered that KOH acted as porogen and had an etching-bridging-reaction effect during the activation process.As a microwave absorber,the composite/paraffin with a filler loading of 16 wt%reaches a minimum reflection loss of−52.8 dB and an effective absorption bandwidth of 4.72 GHz.Moreover,microwave absorption can be maintained within 45 days in air.Compared with untreated MXene,the absorber shows long-term functional stability in an oxygen-containing environment.As for electromagnetic interference shielding,the composite/paraffin at a filler loading of 50 wt%achieves 30.5 dB from 8.0 to 12.4 GHz.Additionally,the heterostructure delivers a desirable specific capacitance of 1,096.3 F g^(−1) at 0.5 A g^(−1).The trifunctional characteristics enrich the application trials of MXene derivatives and satisfy the strong need for versatile materials.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 11074039 and 11004032)the National Basic Research Program of China (Grant No. 2011CBA00200)
文摘Using first-principles calculations within the generalized gradient approximation （GGA） ＋U framework, we inves- tigate the effect of C doping on the structural and electronic properties of LiFePO4. The calculated formation energies indicate that C doped at O sites is energetically favoured, and that C dopants prefer to occupy 03 sites. The band gap of the C doped material is much narrow than that of the undoped one, indicating better electro- conductive properties. To maintain charge balance, the valence of the Fe nearest to C appears as Fe3＋, and it will be helpful to the hopping of electrons.
基金supported bythe Natural Scientific Foundation of China(Grants 21878001,22078002,21776001,21875001,21978002,21808002,22008001,and U1710114).
文摘Rational design and controllable synthesis of practical electrodes with high sta bility and activity at high current density for a hydrogen evolution reaction(HER)are critical for renewable and sustainable energy conversion.However,high-performance TiO_(2)-based electrocatalysts for HER are quite limited,and the cat alytic active centers still remain elusive.Herein,a simple strategy is demonstrated for the synthesis of TiO_(2)-carbon composite(TiO_(2)/C)with high HER performance and stability.The remarkable HER performance of TiO_(2)/C can be ascribed to the doping of carbon atoms,which leads to stronger hybridization of Ti 3d and O 2p orbitals,thus substantially improving the electrocatalytic efficiency.This study elucidates that the hydrogen evolution activity of oxide electrocatalysts can be largely improved by regulating their electronic structures by doping carbon atoms and also provides an effective strategy for designing heterostructured electro catalysts with high catalytic activity and stability at high current density for HER.
基金This research was supported by Guangxi Natural Science Foundation(No.2017GXNSFAA198247).
文摘The electron structure and optical properties of C-TiO_(2)(001)surface under external electric field were studied by DFT method.After carbon doping,a new impurity level is introduced in the bandgap region of TiO_(2)(001)surface,and leads to the decrease of band gap,contributing to the shift of optical absorption to the visible region.When external electric field is applied across the C-TiO_(2)(001)surface,the band gap is further reduced with the increase of the electric field intensity from 0.1 eV to 0.5 eV.The electric field over 0.5 eV induces the electronic polarization.The spin-up bands show a gap,while spin-down electrons correspond to a metallic state.The energy gap of spin-up band decreases with increasing the electric field from 0.7 eV to 1.0 eV.The optical absorption of C-TiO_(2)(001)shifts to long wavelength compared with pure TiO_(2)(001).The electric filed make the optical absorption red-shift further,and the shift increases with an increase of the electric field,especially in the range of 0.7 eV-1.0 eV.The results show that the combined effect of carbon doping and electric field can enhance the photocatalytic activity of TiO_(2)(001)surface in visible region.
文摘The design and development of a highly robust catalyst for energy production and environmental abetment are gaining much attention in the field of visible-light-driven catalysis.This work demonstrates the fabrication of a series of hierarchical macroporous mixed-phase TiO_(2)on the surface of B-doped g-C_(3)N_(4)(BCN).The physicochemical properties such as crystallinity,morphology,chemical environment,and optical and electronic properties of the as-synthesized materials were analysed by using different analytical techniques.PXRD and HRTEM data revealed the growth of mixed-phase TiO_(2)(anatase and rutile)on the BCN surface,mimicking P25 in the case of the best photocatalyst(TBCN-8).The catalytic activity of the as-synthesized materials was tested towards H2O_(2)production(110μmol h-1)and phenol oxidation(87% of 20 ppm phenol solution)under visible light.Higher photocurrent,lower impedance arc,and lower PL intensity suggest a lower electron-hole recombination rate in the case of TBCN-8,elucidating the best catalytic performance by the material.This work validates the facile fabrication of macroporous TiO_(2)/BCN nanocomposites and their visible-light-driven catalytic activity based on both the p-n heterojunction and Z-scheme mechanism.
基金support from the National Natural Science Foundation of China(21671047 and 21871065)the Guangdong Provincial Key Laboratory of Energy Materials for Electric Power(no.2018B030322001).
文摘As a promising hydrogen evolution reaction(HER)electrocatalyst,molybdenum carbide materials have attracted great attention owing to their Pt-like electronic structure.The morphology control of Mo_(2)C usually involves complicated procedures,and porous structures are desirable for electrocatalytic applications.Herein,we present a facile acid-directed synthesis strategy forβ-Mo_(2)C nanoparticles embedded in a nitrogen doped carbon matrix(β-Mo_(2)C/NC)with controllable morphologies through heat treatment of Mo-melamine complexes for electrocatalytic HER applications.It is found that the applied acid can effectively tune the morphology of Mo-melamine complexes,and thus the finalβ-Mo_(2)C/NC materials.With oxalic acid,the as-preparedβ-Mo_(2)C/NC materials possess a porous structure and high surface area(23.3 m^(2)g^(-1)),leading to distinguished electrocatalytic HER activities in both acidic and alkaline media,requiring low overpotentials of 152 and 135 mV vs.reversible hydrogen electrode(RHE)to reach a current density of-10 mA cm^(-2),with a Tafel slope of 58 and 56 mV dec^(-1),respectively.The synthetic route proposed in this work may offer a new thinking for the morphology-controllable synthesis of transition metal carbide materials for heterogeneous(electro)catalysis applications.
基金Project supported by the National Natural Science Foundation of China(No.11274096)the University Science and Technology Innovation Team Support Project of Henan Province(No.13IRTSTHN016)+1 种基金the University key Science Research Project of Henan Province(No.16A140043)supported by the High Performance Computing Center of Henan Normal University
文摘By using a combined method of density functional theory and non-equilibrium Green＇s function formalism,we investigate the electronic transport properties of carbon-doped armchair phosphorene nanoribbons（APNRs）.The results show that C atom doping can strongly affect the electronic transport properties of the APNR and change it from semiconductor to metal.Meanwhile,obvious negative differential resistance（NDR） behaviors are obtained by tuning the doping position and concentration.In particular,with reducing doping concentration,NDR peak position can enter into m V bias range.These results provide a theoretical support to design the related nanodevice by tuning the doping position and concentration in the APNRs.
基金the China Academy of Launch Vehicle Technology(Nos.5120200522 and 5120210234)the National Natural Science Foundation of China(No.21875190)+1 种基金Foundation of Aeronautics Science Fund(No.2020Z056053002)Fundamental Research Funds for the Central Universities(construction and low-frequency microwave absorption properties of metamaterials).
文摘Hierarchical hollow-structured magnetic–dielectric materials are considered to be promising and competitive functional absorbers for microwave absorption(MA).Herein,a hierarchical hollow hydrangea multicomponent metal oxides/metal-carbon was designed and successfully produced via a facile self-assembly method and calcination process.Adequate magnetic NiO and Ni nanoparticles were suspended within the hollow hydrangea-like nitrogen-doped carbon matrix(HH N-NiO/Ni/C),constructing a unique hierarchical hollow structured multicomponent magnetic–dielectric MA composite.The annealing temperature and oxidation time were carefully regulated to investigate the complex permittivity and permeability.HH N-NiO/Ni/C delivers exceptional MA properties with maximum reflection loss of–45.8 dB at 1.7 mm thickness and displays a wide effective absorption frequency range of 5.6 GHz.The superior MA performance can be attributed to the following aspects:(1)The hierarchical hollow multicomponent structure offers plentiful of heterojunction interfaces triggering interfacial polarization;(2)nitrogen doped-carbon(N-C)facilitates the conductive loss by the unique electron migration path in the graphitized C and NiO/Ni;(3)magnetic NiO/Ni nanoparticles homogeneously dispersed within N-C form extensive C skeleton and strengthen the magnetic response ability;(4)hierarchical hollow wrinkled structures possess a large interspace and heterogeneous interface improving polarization loss and enhancing multireflection process and the unique structure satisfies magnetic and dielectric loss simultaneously resulting from synergistic effects of different components within the composites.
基金supported by the Natural Science Foundation of Shandong Province(ZR2021ME194,2022TSG-C2448,and 2023TSGC0545)the Key Research and Dev-elopment Program of Shandong Province(2021ZLGX01).
文摘Enormous endeavors have been made to cope with microwave pollution and energy crisis.Here,porous nitrogen-doped C/TiO_(2) composites with absorption/shielding/supercapacitor functions were derived from MXene/polyaniline.It was discovered that KOH acted as porogen and had an etching-bridging-reaction effect during the activation process.As a microwave absorber,the composite/paraffin with a filler loading of 16 wt%reaches a minimum reflection loss of−52.8 dB and an effective absorption bandwidth of 4.72 GHz.Moreover,microwave absorption can be maintained within 45 days in air.Compared with untreated MXene,the absorber shows long-term functional stability in an oxygen-containing environment.As for electromagnetic interference shielding,the composite/paraffin at a filler loading of 50 wt%achieves 30.5 dB from 8.0 to 12.4 GHz.Additionally,the heterostructure delivers a desirable specific capacitance of 1,096.3 F g^(−1) at 0.5 A g^(−1).The trifunctional characteristics enrich the application trials of MXene derivatives and satisfy the strong need for versatile materials.
